The Separation Of Tidal And Subtidal Currents For Ship-mounted ADCP Data At Summer About Taiwan Strait

Cruising ADCP along the track can get the quasi-continuous flow of vertical profile data, and spatial structure of ocean currents in a relatively low price. The ocean currents observed from cruising ADCP includes tidal currents and some other high frequency currents especially in coastal area. The tidal currents signals account for more than 50%. These signals will conceal the low frequency currents, so the tidal currents should be separated before analysis. Once the tidal currents separated from the ocean currents, the spatial structure of ocean currents is avaiable to analysis ocean currents such as the Kuroshio, flow field dynamics and kinematics. So cruising ADCP flow separation method has a wide range of applications.Based on separation of tidal and subtidal method developed by Candela et al in 1992, current measurements obtained from ship-mounted Acoustic Doppler Current Profiler (ADCP) and submerged buoy in summer 2006 were used to analyze fifteen cross-shelf transects in Taiwan Strait. Through the comparisons of the results calculated with and without the submerged data, the result is that former is better. Compared with one-month submerged buoy current data, the relative errors of current velocity and direction calculated from the former results which are less than 0.5 account for 77% and 72% of one-month submerged buoy data, respectively, however, both of the relative errors of current velocity and direction of the latter less than 0.5 account for 48% of buoy data.Only cruising obsevation data is used in the traditional method to separate residual current and tidal current. Through the analysis and comparison, the calculation using some more sub-surface buoys data is better. The Candela method is accessable to separate the residual current and tidal current but which is insufficient. The primary functions in Candela methods should be further improved or a new better method is proposed.